Multilayer interventional catheter

ABSTRACT

The catheter comprises a catheter tube formed of two superposed tubular layers of materials which differ from one another. A tubular mediator layer is arranged between the layers to provide an adhesive anchorage for the layers.

BACKGROUND OF THE INVENTION

[0001] This invention relates to an interventional catheter comprising acatheter tube having two superposed layers of materials secured togetherand with mechanical properties differing from one another, a guidewirelumen in the catheter tube for the sliding fit of a guidewire, and aballoon with a distal end sealingly surrounding the catheter tubewhereby the catheter tube has an inner layer forming the guidewire lumenand an outer layer forming an outer surface of the catheter tube.

[0002] Over the wire catheters have been widely used for interventionssuch as percutaneous transluminal cardiovascular angioplasty. A problemwith these catheters is that the guidewire may clog into the guidewirelumen of the catheter, whereby the guidewire may follow the balloon uponwithdrawal thereof after the inflation procedure thereby making itnecessary to re-insert the guidewire into the treated area of the bloodvessel for repositioning a balloon therein in case a second inflation isneeded. A further problem is that the catheter has to achieve anacceptable compromise between the requirements of some stiffness toassure good pushability and some flexibility to assure kink resistance.In addition, the catheter has to permit safe attachment of the balloonto the catheter tube.

[0003] Monorail® technology, which provides for an entry of theguidewire distal of the balloon and an exit for the guidewire distal ofthe proximal end of the catheter tube, substantially reduces the risk ofthe guidewire clogging in the guidewire lumen because the length offrictional engagement between the guidewire and the guidewire lumen isstrongly reduced. That is also of great help in the handling of ballooncatheters for balloon exchange purposes. Though limited, the frictionand clogging problem is, however, still existent.

[0004] Two layer catheter shafts have been developed. For example, thedocument WO 92/11893 describes an intra-aortic balloon apparatuscomprising a hollow catheter in which is located an elongated memberforming a central lumen extending out of the catheter at the distal endthereof. An aortic pumping balloon is positioned over the elongatedmember; the distal end of the balloon is bonded to a tip affixed to thedistal end of the elongated member, and its proximal end is bonded tothe distal end of the catheter. In order to achieve a balance offlexibility and remains and to avoid kinking, the elongated member isformed of an inner layer comprised of a soft elastomeric material toimpart flexibility to the tubing and the outer layer is comprised of ahard plastic material to impart structural support to the elongatedmember. This balloon apparatus cannot be loaded with a guidewire andmoved into tortuous vessels with the guidewire loaded inside theelongated member as the friction between guidewire and elongated memberincreases distinctively when the elongated member is shaped into curves.There would be therefore the risk that a spiral wound guidewire could becaptured in the soft elastomeric plastic material of the inner layer ofthe elongated member. Although the outer layer of the elongated memberthat is coextruded onto the inner layer is formed of nylon, a materialwhich is expected to be directly weldable to a wide variety ofmaterials, this balloon apparatus cannot be introduced into narrowvessels or narrow stenoses, nor can it be passed through narrowpunctures to enter the blood vessels. This is because of the relativelylarge profile of the folded balloon, due to the distal fixture of theballoon to the elongated member. The balloon is bonded to anintermediate tip element which in turn is bonded to the elongatedmember.

[0005] The document EP 0 650 740 A1 shows a catheter comprising acatheter tube having two superposed layers of materials secured inrelation to one another and with mechanical properties differing fromone another, a longitudinal lumen in the catheter tube for the slidingfit of a guidewire, and a balloon with a proximal end and a distal end,the distal end sealingly surrounding the catheter tube, whereby thecatheter tube has an inner layer forming the longitudinal lumen and anouter layer forming the outer surface of the catheter tube. In thiscatheter, the inner layer is formed of a material with lower frictioncoefficient than the material forming the outer layer, whereby there isno more risk of having the guidewire clogging in the guidewire lumen ofthe catheter tube.

[0006] In terms of two layers catheter shafts, it has been observed thatin practical use the adhesion of the two layers of material was notabsolutely satisfactory. Although the coextrusion technology currentlyused for making such catheter shafts seems to involve close molecularinterpenetration of the materials forming the superposed layers of theshaft, it has been possible to observe separation of the two layers, forexample at the place of insertion of the shaft over the guidewire.Furthermore, tear test effected on such structures has shown that thetwo layers can separate under extreme conditions of stress on the shaft.

[0007] It is an object of this invention to propose an interventionalballoon catheter avoiding the aforesaid drawbacks A further object ofthe invention is an interventional catheter structure which is versatileand which provides a fully controllable and easy to manufactureassembly. Still a further object of the invention is an interventionallow profile balloon catheter that can be safely operated on a guidewireand moved into tortuous vessels and other extreme conditions.

[0008] Various multilayer catheters are known in the art. Reference ismade to U.S. Pat. Nos. 4,627,844; 4,636,346; 5,403,292; 5,499,973; and5,538,510.

[0009] All documents cited herein, including the foregoing, areincorporated herein by reference in their entireties for all purposes.

SUMMARY OF THE INVENTION

[0010] Accordingly, where the catheter comprises mediator layer meansarranged between the inner layer and the outer layer for the adhesiveanchorage of the layers thereto, securing of the inner layer and outerlayer is strongly enhanced independently of their intrinsic capacity ofadhesion to one another. The risk of a poor adhesion or the risk of afailure in the adhesion of the two layers to one another is eliminated.The inner and outer layers may be chosen for their most appropriatemechanical characteristics rather than for their capacity to adhere toone another. Because of the adhesive anchorage of the inner and outerlayers on the mediator layer means, the risk of separation of the twolayers upon insertion of the catheter tube over a guidewire isminimized. And the assembly of inner and outer layers is under controland the possibilities of changing the flexibility of the assembly areimproved; due to the adhesive anchorage on the mediator layer means,rigidity of the assembly is enhanced with the same basic inner and outerlayers, whereas flexibility of the assembly may be mastered by safelyacting on the thickness of the inner and outer layers, with theresulting reduction in the profile of the catheter. As a result of theadhesive anchorage of the inner and outer layers on the mediator layermeans the assembly behaves like a unit; accordingly, the assembly may besafely grabbed by the outer layer and tear tests are thus facilitated.

[0011] The inner and outer layers and the mediator layer means may becongruent in length, so that the catheter shaft can be produced in longtubes which may be cut at will to the appropriate length. Where theinner layer, the mediator layer means and the outer layer arecoextruded, a catheter tube is formed in a continuous process avoidingthe need of using a core in the inner layer.

[0012] Where the inner and outer layers are substantially transparentand the mediator layer means are contrasted with respect to thesubstantially transparent inner and outer layers, a visual control ofthe assembly is readily available to further improve the manufacture.

[0013] Where the mediator layer means have mechanical propertiesdiffering from the mechanical properties of the inner and outer layers afurther step is achieved in the possibility of changing the lengthwiseflexibility properties of the catheter.

[0014] When the inner layer is formed of a material with lower frictioncoefficient than the material forming the outer layer, there is no morerisk of having the guidewire clogging or being captured in the guidewirelumen of the catheter tube. Withdrawal and re-positioning of the ballooncatheter on a guidewire left in place at the site of treatment in thevessel system is rapid, safe and precise. Furthermore, the choice can bemade for materials for the inner and outer layers having the mostappropriate friction and kink resistance coefficients, while safeattachment of the balloon may be made at will on the outer layer whichis chosen without being influenced by the friction properties of theinner layer.

[0015] The mediator layer means may be formed on the basis of a lowdensity polyethylene to offer superior adhesion performance in a widevariety of configurations of the inner and outer layers and ease ofprocessing on conventional fabrication equipment.

[0016] In a preferred form of the invention, the inner layer is made ofa polyethylene or of a high density polyethylene, both of which assurean extremely low friction coefficient and an appropriate kink resistancecoefficient. In another preferred form of the invention, the outer layeris made of a polyamid to assure easy welding of the balloon and a goodstiffness at that level.

[0017] In sum, the invention relates to an interventional cathetercomprising a catheter tube having two superposed layers of materialssecured together and with mechanical properties differing from oneanother. A guidewire lumen is formed in the catheter tube for thesliding fit of a guidewire, and a balloon with a distal end sealinglysurrounding the catheter tube. The catheter tube has an inner layerforming the guidewire lumen and an outer layer forming an outer surfaceof the catheter tube wherein it comprises mediator layer means arrangedbetween the inner layer and the outer layer for the adhesive anchorageof the layers thereto. The inner and outer layers and the mediator layermeans may be congruent in length. The inner layer, the mediator layermeans, and the outer layer may be coextruded. The inner and outer layersmay be substantially transparent and the mediator layer means may becontrasted with respect to the substantially transparent inner and outerlayers. The mediator layer means may have mechanical propertiesdiffering from mechanical properties of the inner and outer layers. Theinner layer may be formed of a material with lower friction coefficientthan the material forming the outer layer. The mediator layer means maybe formed on the basis of a low density polyethylene. The inner layermay be made of a polyethylene. The inner layer may be made of a highdensity polyethylene. The outer layer may be made of a polyamid.

[0018] These and other objects, features and advantages of the inventionwill become readily apparent from the following description withreference to the accompanying drawings which show, diagrammatically andby way of example only, preferred but still illustrative embodiments ofthe invention.

[0019] As will be realized, the invention is capable of other anddifferent embodiments and methods of construction, and its severaldetails are capable of modification in various obvious respects, allwithout departing from the invention. Accordingly, the drawing anddescription are to be regarded as illustrative in nature, and not asrestrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a longitudinal cross-sectional view of an over the wireballoon catheter embodying the invention;

[0021]FIG. 2 is a longitudinal cross-sectional view of a Monorail®balloon catheter embodying the invention; and

[0022]FIG. 3 is an enlarged cross-sectional view of a variant catheterembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The interventional catheter shown in FIG. 1 comprises a cathetertube 1 formed of two superposed tubular layers of materials 2 and 3 witha tubular mediator layer 4 arranged therebetween for the adhesiveanchorage of the layers 2 and 3 onto the mediator layer 4.

[0024] The tubular layers 2, 3 and 4 extend all over the length ofcatheter tube 1, being thus congruent in length, and the assembly oflayers forming the catheter tube 1 may be obtained by the knowncoextrusion technology, i.e., by extruding simultaneously the innerlayer 2 with the mediator layer 4 and with the outer layer 3 thereover.Layers 2 and 3 have mechanical properties differing from one anotherand, preferably, mediator layer 4 also has mechanical propertiesdiffering from the mechanical properties of inner and outer layers 2 and3.

[0025] Preferably, the inner layer 2 is formed of a material with lowerfriction coefficient than the material forming the outer layer 3. Forexample, the inner layer 2 may be formed of a polyethylene, preferably ahigh density polyethylene, whereas the outer layer 3 may be formed of apolyamid. The mediator layer 4 may be formed on the basis of a lowdensity polyethylene.

[0026] Preferably, the inner and outer layers 2 and 3 are substantiallytransparent, whereas the mediator layer 4 is contrasted with respect tothe substantially transparent inner and outer layers 2 and 3.

[0027] The catheter tube I has thus a longitudinal lumen 5 for thesliding fit of a guidewire exemplified by dotted line 6, which lumen 5has a very low friction coefficient, lower than that of the outer layer3, and a non-kinking capacity while the outer layer 3 forms an outersurface of the catheter tube 1 and is easily weldable to the materialscommonly used for making balloons for angioplasty purposes and the like.And therebetween, the mediator layer 4 assures the best adhesiveanchorage of inner and outer layers 2 and 3 thereto, the catheter tube 1thus behaving as a unitary element with differentiating properties atits inner and outer levels.

[0028] Over the distal portion of the catheter tube I is positioned aballoon 7 the distal end 8 of which sealingly surrounds the outer layer3 of catheter tube 1, for example by welding.

[0029] A tube 9 is arranged over the catheter tube 1, at a radialdistance thereof, thus defining an inflation lumen 10 for the balloon 7.The proximal end 11 of the balloon 7 is welded onto the distal end oftube 9.

[0030] The interventional catheter shown in FIG. 2 also comprises acatheter tube 12 having two superposed tubular layers of materials 13and 14 with a tubular mediator layer 15 arranged therebetween foradhesive anchorage of the layers 13 and 14 onto the mediator layer 15.

[0031] The tubular layers 13, 14 and 15 extend all over the cathetertube 12 and the assembly of layers forming the catheter tube 12 may alsobe obtained by the known coextrusion technology whereby inner tubularlayer 13 is extruded simultaneously with the mediator layer 15 and theouter layer 14 thereover. Layers 13 and 14 have mechanical propertiesdiffering from one another and, preferably, mediator layer 15 also hasmechanical properties differing from the mechanical properties of innerand outer layers 13 and 14.

[0032] Preferably the inner layer 13 is made of a material with lowerfriction coefficient than the material forming the outer layer 14. Forexample, inner layer 13 may be formed of a polyethylene, preferably ahigh density polyethylene, whereas the outer layer 14 may be made of apolyamid. The mediator layer 15 may be formed on the basis of a lowdensity polyethylene.

[0033] Preferably the inner and outer layers 13 and 14 are substantiallytransparent and the mediator layer 15 is contrasted with respect to thesubstantially transparent inner and outer layers 13 and 14.

[0034] The catheter tube 12 has thus a longitudinal lumen 16 for thesliding fit of a guidewire exemplified by dotted line 17, which lumen 16has a very low friction coefficient, lower than that of the outer layer14 and with a non-kinking capacity, whereas outer layer 14 forms anouter surface of the catheter tube 12 and is easily weldable to thematerials currently used for making angioplasty balloons. Andtherebetween, the mediator layer 15 also assures superior adhesiveanchorage for inner and outer layers 13 and 14, the catheter tube 12acting as a unit with different properties at its inner and outerlevels.

[0035] A tube 18 is affixed, for example welded, in parallelrelationship to the proximal portion of catheter tube 12, and this tube18 extends proximally of the catheter tube 12. The tube 18 defines aninflation lumen 19 for a balloon 20 the distal end 21 of which sealinglysurrounds the outer layer 14 of catheter tube 12, for example bywelding. The proximal end 22 of balloon 20 sealingly surrounds aproximal portion of the catheter tube 12 and a distal portion of tube18, whereby the proximal portion of catheter tube 12 extends proximallyout of the balloon 20 and the distal portion of tube 18 extends withinthe balloon 20.

[0036] Variants are readily available. For example, the mediator layermay be made of two superposed tubular layers of materials which differfrom one another in order to respectively provide superior adhesiveanchorage for the inner and outer layers while assuring total adhesiveanchorage between them. This configuration is advantageous for exampleto match particular flexibility requirements for the catheter tube or toassume adhesive anchorage conditions which would be otherwise difficultfor the inner and outer layers.

[0037]FIG. 3 shows such a configuration where the catheter tube 23 isformed of two superposed tubular layers of materials 24 and 25 with atubular mediator layer 26 arranged therebetween and formed of twosuperposed adhesively anchored tubular layers 27 and 28, layer 27 beingfor adhesive anchorage of inner layer 24 and layer 28 for adhesiveanchorage of outer layer 25. Within inner layer 24 is the guidewirelumen 29 for the sliding fit of a guidewire exemplified by dotted line30.

[0038] It will be evident from considerations of the foregoing that theMultilayer Interventional Catheter is now available, and may beconstructed using a number of methods and materials, in a wide varietyof sizes and styles for the greater efficiency and convenience of auser.

[0039] The above described embodiments of the invention are merelydescriptive of its principles and are not to be considered limiting.Further modifications of the invention herein disclosed will occur tothose skilled in the respective arts and all such modifications aredeemed to be within the scope of the invention as defined by thefollowing claims.

1. An interventional catheter comprising: a catheter tube having twosuperposed layers of materials secured together and with mechanicalproperties differing from one another, a guidewire lumen in the cathetertube for the sliding fit of a guidewire, and a balloon with a distal endsealingly surrounding the catheter tube, whereby the catheter tube hasan inner layer forming the guidewire lumen and an outer layer forming anouter surface of the catheter tube, wherein it comprises mediator layermeans arranged between the inner layer and the outer layer for theadhesive anchorage of the layers thereto.
 2. The interventional catheteraccording to claim 1 wherein the inner and outer layers and the mediatorlayer means are congruent in length.
 3. The interventional catheteraccording to claim 1 wherein the inner layer, the mediator layer means,and the outer layer are coextruded.
 4. The interventional catheteraccording to claim 1 wherein the inner and outer layers aresubstantially transparent and the mediator layer means are contrastedwith respect to the substantially transparent inner and outer layers. 5.The interventional catheter according to claim 1 wherein the mediatorlayer means have mechanical properties differing from mechanicalproperties of the inner and outer layers.
 6. The interventional catheteraccording to claim 1 wherein the inner layer is formed of a materialwith lower friction coefficient than the material forming the outerlayer.
 7. The interventional catheter according to claim 1 wherein themediator layer means are formed on the basis of a low densitypolyethylene.
 8. The interventional catheter according to claim 1wherein the inner layer is made of a polyethylene.
 9. The interventionalcatheter according to claim 1 wherein the inner layer is made of a highdensity polyethylene.
 10. The interventional catheter according to claim1 wherein the outer layer is made of a polyamid.